Semiconductor devices having electro-optical substrates

ABSTRACT

Memory devices having electro-optical substrates are described herein. In one embodiment, a memory device includes a plurality of memories carried by an electro-optical substrate. The electro-optical substrate can include a circuit board and an optical routing layer on the circuit board. The memories can be (a) electrically coupled to the circuit board and (b) optically coupled to the optical routing layer. In some embodiments, the optical routing layer is a polymer waveguide.

CROSS-REFERENCE TO RELATED APPLICATION

This application contains subject matter related to an U.S. Patent Application by Omar J. Bchir, titled “SEMICONDUCTOR PACKAGES HAVING PHOTON INTEGRATED CIRCUIT (PIC) CHIPS.” The related application, of which the disclosure is incorporated by reference herein, is assigned to Micron Technology, Inc., and is identified as U.S. patent application Ser. No. 16/172,624, filed on Oct. 26, 2018.

TECHNICAL FIELD

The present disclosure generally relates to semiconductor devices having optical interfaces, and more particularly relates to memory devices including electro-optical substrates.

BACKGROUND

Memory packages or modules typically include multiple memory devices mounted on a substrate. Memory devices are widely used to store information related to various electronic devices such as computers, wireless communication devices, cameras, digital displays, and the like. Information is stored by programming different states of a memory cell. Various types of memory devices exist, including magnetic hard disks, random access memory (RAM), read only memory (ROM), dynamic RAM (DRAM), synchronous dynamic RAM (SDRAM), and others.

In some instances, such as in data centers or high-performance computers, many memory devices are operatively coupled together (e.g., in server racks). More specifically, individual memory devices can be electrically coupled together via conductive (e.g., copper) cables or traces. In some instances, the electrically conductive cables or traces are further coupled to optical transceivers that convert electrical signals into optical signals that can be routed at high speeds and bandwidths, for example, between different locations in a data center. Such optical transceivers can be relatively expensive. Moreover, at high data bandwidths the electrical signals in the conductive cables or traces can only propagate for small distances until additional repeater chips are needed to boost the signals. Such repeater chips consume additional power-increasing the cost of operating a data center, high-performance computer, or other device including many interconnected memory devices.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the present technology can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale. Instead, emphasis is placed on clearly illustrating the principles of the present technology.

FIGS. 1A and 1B are partially schematic side cross-sectional and top views, respectively, of a semiconductor package configured in accordance with an embodiment of the present technology.

FIG. 2 is a partially schematic top view of a semiconductor package configured in accordance with another embodiment of the present technology.

FIG. 3 is a partially schematic top view of a semiconductor package configured in accordance with another embodiment of the present technology.

FIG. 4 is a front view of a memory device configured in accordance with an embodiment of the present technology.

FIG. 5A is a partially schematic front view of a memory device configured in accordance with another embodiment of the present technology and having an electro-optical substrate.

FIG. 5B is a side cross-sectional view of a portion of the electro-optical substrate shown in FIG. 5A.

FIG. 6 is a schematic view of a system that includes a semiconductor package and/or memory device configured in accordance with embodiments of the present technology.

DETAILED DESCRIPTION

Specific details of several embodiments of semiconductor devices including electro-optical substrates, and associated systems and methods, are described below with reference to FIGS. 1-6. In several of the embodiments, a semiconductor device such as a memory device (e.g., a dual in-line memory module (DIMM)), includes an electro-optical substrate comprising a polymer waveguide formed on a circuit board (e.g., a printed circuit board). The electro-optical substrate can carry a plurality of memories, and the memories can be electrically coupled to the circuit board and optically coupled to polymer waveguide. The memories can be configured to receive power via the circuit board and to receive, transmit, or both receive and transmit optical signals (e.g., data signals) via the polymer waveguide.

Accordingly, memory devices in accordance with the present technology can include an integrated waveguide or other optical layer that provides an optical in/out (I/O) interface for the memory device. In contrast, many conventional memory devices have electrical I/O interfaces. To incorporate such conventional memory devices into an optical memory system (e.g., some data centers or high-performance computers), the electrical signals must be routed to electro-optical transceivers that are positioned external to the memory devices (e.g., at the box or rack level in a data center). Thus, the present technology can reduce or eliminate the need for such electro-optical transceivers in the data path-reducing costs, complexity, and/or power consumption. Moreover, by reducing the amount of conductive metal (e.g., copper wires, traces, etc.) in the data path, the present technology can reduce or eliminate the need for repeater chips or other components for boosting signal strength and/or integrity during data transmission at high bandwidths-further reducing costs, complexity, and/or power consumption.

Numerous specific details are discussed to provide a thorough and enabling description of embodiments of the present technology. A person skilled in the art, however, will understand that the technology may have additional embodiments and that the technology may be practiced without several of the details of the embodiments described below with reference to FIGS. 1-6. In other instances, well-known structures or operations often associated with memory devices are not shown, or are not described in detail, to avoid obscuring other aspects of the technology. In general, it should be understood that various other devices and systems in addition to those specific embodiments disclosed herein may be within the scope of the present technology. For example, in the many of the embodiments below, the memory devices and systems are described in the context of DRAM and flash (e.g., NAND and/or NOR) storage media, and DIMMs compatible with DRAM and flash storage media. Memory devices and systems configured in accordance with other embodiments of the present technology, however, can include memory modules compatible with other types of storage media, including PCM, RRAM, MRAM, read only memory (ROM), erasable programmable ROM (EPROM), electrically erasable programmable ROM (EEROM), ferroelectric, magnetoresistive, and other storage media, including static random-access memory (SRAM). Additionally, the present technology can be used in semiconductor devices other than memory devices.

As used herein, the terms “vertical,” “lateral,” “upper,” “lower,” “above,” and “below” can refer to relative directions or positions of features in the semiconductor devices in view of the orientation shown in the Figures. For example, “upper” or “uppermost” can refer to a feature positioned closer to the top of a page than another feature. These terms, however, should be construed broadly to include semiconductor devices having other orientations, such as inverted or inclined orientations where top/bottom, over/under, above/below, up/down, and left/right can be interchanged depending on the orientation.

Unless the context indicates otherwise, structures disclosed herein can be formed using conventional semiconductor-manufacturing techniques, and stages of the methods used to form the structures can be performed at the wafer level or at the die level. Materials can be deposited, for example, using chemical vapor deposition, physical vapor deposition, atomic layer deposition, spin coating, and/or other suitable techniques. Similarly, materials can be removed, for example, using plasma etching, wet etching, chemical-mechanical planarization, or other suitable techniques.

FIGS. 1A and 1B are partially schematic side cross-sectional and top views, respectively, of a semiconductor device or package 100 (“package 100”) configured in accordance with an embodiment of the present technology. Referring to FIGS. 1A and 1B together, the package 100 includes a semiconductor die 110, a first photon integrated circuit (PIC) chip 120, and a second PIC chip 130 each coupled to (e.g., carried by, mounted on, etc.) a package substrate 102. The package substrate 102 can include an interposer, a printed circuit board, a dielectric spacer, another semiconductor die (e.g., a logic die), or another suitable substrate. In some embodiments, the semiconductor die 110 and the first and second PIC chips 120, 130 can be coupled to the package substrate 102 via first through third die-attach materials 103 a-103 c, respectively. In some embodiments, the semiconductor die 110 and/or the PIC chips 120, 130 can be electrically coupled to the substrate via wirebonds (not shown in FIGS. 1A and 1B), conductive interconnects (e.g., in a flip-chip arrangement), or other suitable structures known in the art. In certain embodiments, the semiconductor die 110 and/or the PIC chips 120, 130 are electrically coupled to the package substrate 102 for receiving power via the package substrate 102. As described in greater detail below, in-out (I/O) data communication to the semiconductor die 110 can be provided via a separate electro-optical path that is independent of any electrical connection to the package substrate 102. Moreover, while the semiconductor die 110 is shown positioned laterally between the PIC chips 120, 130 in FIGS. 1A and 1B, in other embodiments, the semiconductor die 110 and the PIC chips 120, 130 can be positioned differently on the package substrate 102. For example, the PIC chips 120, 130 can be positioned adjacent to the same side of the semiconductor die 110, the PIC chips 120, 130 can be positioned adjacent to orthogonal sides of the semiconductor die 110, etc.

In the illustrated embodiment, the semiconductor die 110 includes first bond pads 112 a and second bond pads 112 b arranged on opposing sides of the semiconductor die 110. The first PIC chip 120 includes bond pads 122 and the second PIC chip 130 includes bond pads 132. The semiconductor die 110 is electrically coupled to (i) the first PIC chip 120 via first wirebonds 104 a extending between and electrically connecting the bond pads 122 of the first PIC chip 120 and the first bond pads 112 a of the semiconductor die 110, and (ii) the second PIC chip 130 via second wirebonds 104 b extending between and electrically connecting the bond pads 132 of the second PIC chip 130 and the second bond pads 112 b of the semiconductor die 110. In other embodiments, the bond pads 112 a, 112 b, 122, and/or 132 can have different configurations, shapes, placements, etc., and/or the semiconductor die 110 can be electrically coupled to the PIC chips 120, 130 via other suitable methods. In some embodiments, for example, the semiconductor die 110 can be electrically coupled to the PIC chips 120, 130 via the package substrate 102 (e.g., via conductive traces in and/or on the package substrate 102), via direct-chip attach methods (e.g., via conductive pillars, studs, etc., in a stacked arrangement), etc.

The semiconductor die 110 includes integrated circuitry 114 (shown schematically) such as, for example, integrated memory circuitry and/or logic circuitry, which can include various types of semiconductor components and functional features, such as dynamic random-access memory (DRAM), static random-access memory (SRAM), flash memory, other forms of integrated circuit memory, processing circuits, and/or other semiconductor features. In the illustrated embodiment, the semiconductor die 110 further includes analog driver circuitry 116 (shown schematically) for converting digital signals within the semiconductor die 110 to analog signals, as described in greater detail below. In some embodiments, the analog driver circuitry 116 can be provided on a separate semiconductor die from the integrated circuitry 114 (e.g., as illustrated in FIG. 3).

The first PIC chip 120 includes integrated circuitry 124 (shown schematically) and the second PIC chip 130 includes integrated circuitry 134 (shown schematically) that can be formed on and/or in a substrate (e.g., a silicon substrate, indium phosphide (InP) substrate, electro-optic crystal-based substrate, etc.). In general, the integrated circuitry 124, 134 includes photon integrated circuitry that can incorporate multiple photonic functions and/or devices such as, for example, wavelength-division multiplexers (WDM), arrayed waveguide gratings (AWG), optical filters, optical amplifiers, optical modulators, photodiodes, light sources (e.g., lasers), optical detectors, etc. The second PIC chip further includes a light source 136—such as a laser—that can be externally driven to modulate light generated by the light source 136. In some embodiments, the light source 136 can be formed as part of the integrated circuitry 134 or otherwise on and/or in the second PIC chip 130 while, in other embodiments, the light source 136 can be a separate chip or component that is (i) electrically coupled to the semiconductor die 110 directly (e.g., via the second wirebonds 104 b) and/or indirectly (e.g., via an electrical connection to the second PIC chip 130), and (ii) optically coupled to the second PIC chip 130. In some embodiments, for example, the light source 136 can be a separate chip or component that is soldered to the second PIC chip 130.

In the illustrated embodiment, an array of first optical fibers 106 a are optically coupled to the first PIC chip 120, and an array of second optical fibers 106 b are optically coupled to the second PIC chip 130. The optical fibers 106 a, b are configured to optically couple the PIC chips 120, 130 to external devices, systems, etc., such as other semiconductor devices in a data center. The optical fibers 106 a, b can be optically coupled to the PIC chips 120, 130 through an edge connection, a butt connection, or another suitable connection known in the art. For example, in an edge connection configuration, the substrates of the PIC chips 120, 130 can be etched to include gutters or grooves (e.g., v-grooves), and the optical fibers 106 a, b can be positioned within the grooves such that the optical fibers 106 a, b are optically coupled to the integrated circuitry 124, 134 (e.g., aligned with waveguides of the integrated circuitry 124, 134). In some embodiments, an optically transparent epoxy and/or a refractive index matching gel can be used to close any gaps between the optical fibers 106 a, b and the PIC chips 120, 130. In a butt connection configuration, the optical fibers 106 a, b can be positioned generally perpendicular to the PIC chips 120, 130 and optically coupled to the integrated circuitry 124, 134 via optical gratings (e.g., vertical grating couplings). While four first optical fibers 106 a and four second optical fibers 106 b are shown in FIG. 1B, the package 100 can include any number of optical fibers. For example, the integrated circuitry 124 of the first PIC chip 120 and/or the integrated circuitry 134 of the second PIC chip 130 can include optical (de)multiplexers such that a single first optical fiber 106 a and/or a single second optical fiber 106 b can be used to transmit/receive optical signals from the PIC chips 120, 130 (e.g., as shown FIG. 3). Likewise, the package 100 can include more than four optical fibers 106 a, b (e.g., where the semiconductor die 110 has a higher bandwidth) and/or the package 100 can include multiple ones of the PIC chips 120, 130.

In operation, the first PIC chip 120 and the first optical fibers 106 a comprise a receive side or receive function of the package 100. Specifically, the first PIC chip 120 is configured to (i) receive optical signals (e.g., data signals) from a source that is external to the package 100 (e.g., a device in a data center that is external to the package 100) over the first optical fibers 106 a, (ii) convert the optical signals into electrical signals (e.g., via the integrated circuitry 124 of the first PIC chip 120), and (iii) transmit the electrical signals to the semiconductor die 110 (e.g., via the first wirebonds 104 a). Conversely, the second PIC chip 130 and the second optical fibers 106 b comprise a transmit side or transmit function of the package 100. Specifically, the analog driver circuitry 116 of the semiconductor die 110 is configured to convert digital electrical signals within the semiconductor die 110 to analog electrical signals and transmit the analog signals to the second PIC chip 130 (e.g., via the second wirebonds 104 b). The analog electrical signals drive the light source 136 to produce optical signals (e.g., data signals) that can be transmitted from the package 100 over the second optical fibers 106 b. Put differently, the analog driver circuitry 116 of the semiconductor die 110 operates to modulate light produced by the light source 136 of the second PIC chip 130.

Accordingly, the package 100 is configured to both receive and transmit optical signals. In contrast, many conventional semiconductor packages are configured to receive and transmit electrical signals (e.g., via package contacts that provide an electrical connection to external devices). Incorporating such conventional semiconductor packages into an optical I/O system—such as a data center including optical switches and server packages or some high-performance computer—requires connecting electro-optical transceivers to the semiconductor packages via electrically conductive lines such as copper wires or traces. Such electro-optical transceivers require additional power to operate, and can be relatively expensive. Likewise, at high data bandwidths (e.g., about 28 Gbps or greater), the electrical signals from the semiconductor packages can degrade over short transmission distances (e.g., less than about 1 meter) along the conductive lines. Therefore, repeater chips and/or other signal-amplifying or boosting components must be added to the signal path to preserve the integrity of the electrical signals. Again, such components can be expensive and increase power consumption. The present technology therefore reduces costs, complexity, and power consumption compared to conventional systems by converting electrical signals to optical signals at the package level.

In some embodiments, all I/O data signals to the semiconductor die 110 are provided via the PIC chips 120, 130 rather than, for example, from an electrical source coupled to the package substrate 102. However, in other embodiments, the package 100 can include only the first PIC chip 120 and/or the second PIC chip 130 such that the package 100 is configured to (i) receive optical signals (e.g., via the first PIC chip 120) and transmit electrical signals or (ii) receive electrical signals and transmit optical signals (e.g., via the second PIC chip 130). Moreover, in some embodiments, the package 100 can further include other structures or features such as, for example: (i) a casing such as a thermally conductive casing that encloses the semiconductor die 110, the PIC chips 120, 130, the wirebonds 104 a, b, and/or the optical fibers 106 a, b within an enclosure, and/or (ii) an encapsulant deposited or otherwise formed around, over, and/or between the semiconductor die 110, the PIC chips 120, 130, the wirebonds 104 a, b, and/or the optical fibers 106 a, b.

FIG. 2 is a partially schematic top view of a semiconductor device or package 200 (“package 200”) configured in accordance with another embodiment of the present technology. The package 200 can include features generally similar to the features of the package 100 described in detail above. In the illustrated embodiment, however, the package 200 includes a stack 205 of the semiconductor dies 110 carried by a package substrate 202. A plurality of the first PIC chips 120 are coupled to the package substrate 202 and electrically coupled to at least one of the semiconductor dies 110 in the stack 205 via first wirebonds 204 a. Likewise, a plurality of the second PIC chips 130 are coupled to the package substrate 202 and electrically coupled to at least one of the semiconductor dies 110 in the stack 205 via second wirebonds 204 b.

In some embodiments, one of the first PIC chips 120 and one of the second PIC chips 130 can be coupled to each of the semiconductor dies 110 in the stack 205 (e.g., the number of semiconductor dies 110, first PIC chips 120, and second PIC chips 130 can be the same). In the illustrated embodiment, for example, the stack 205 can include four semiconductor dies 110 each coupled to a single one of the first PIC chips 120 and a single one of the second PIC chips 130. In other embodiments, more than one of the first PIC chips 120 and/or more than one of the second PIC chips 130 can be coupled to individual ones of the semiconductor dies 110 (e.g., the number of first PIC chips 120 and/or the number of second PIC chips 130 can be greater than the number of semiconductor dies 110), or individual ones of the PIC chips 120, 130 can be coupled to more than one of the semiconductor dies 110 (e.g., the number of semiconductor dies 110 can be greater than the number of first PIC chips 120 and/or the number of second PIC chips 130).

In operation, the package 200 is configured to receive/transmit optical signals as described in detail above with reference to FIGS. 1A and 1B. For example, the first PIC chips 120 can (i) receive first optical signals from an external source via an array of the first optical fibers 106 a, (ii) convert the first optical signals to electrical signals (e.g., via the integrated circuitry 124 of the individual first PIC chips 120), and (iii) transmit the electrical signals to respective ones of the semiconductor dies 110 in the stack 205 (e.g., via the first wirebonds 204 a). Similarly, the analog driver circuitry 116 of the semiconductor dies 110 operates to convert digital signals from the integrated circuitry 114 of the semiconductor dies 110 to analog electrical signals and transmit the analog electrical signals to respective ones of the second PIC chips 130 (e.g., via the second wirebonds 204 b). The analog electrical signals drive the light sources 136 of the second PIC chips 130 to modulate light signals for transmission from the package 200 via an array of the second optical fibers 106 b.

One of skill in the art will understand that the various functionalities, components, and/or devices of the embodiments illustrated in FIGS. 1A-2 can be combined and/or separated without deviating from the scope of the present technology. FIG. 3, for example, is a partially schematic top view of a semiconductor device or package 300 (“package 300”) configured in accordance with another embodiment of the present technology. The package 300 can include features generally similar to the features of the semiconductor packages 100 and 200 described in detail above. For example, the package 300 includes (i) a plurality of first semiconductor dies 310 arranged in a stack 305 on a package substrate 302, (ii) a plurality of first PIC chips 320 coupled to the package substrate 302 and electrically coupled to at least one of the first semiconductor dies 310 in the stack 305 via first wirebonds 304 a, and (iii) a plurality of second PIC chips 330 coupled to the package substrate 302. Similarly, first optical fibers 306 a are optically coupled to the first PIC chips 320 and second optical fibers 306 b are optically coupled to the second PIC chips 330.

In the illustrated embodiment, individual ones of the first semiconductor dies 310 can include the integrated circuitry 114. However, the package 300 further includes a plurality of second semiconductor dies 340 each including the analog driver circuitry 116. That is, compared to the embodiments illustrated in FIGS. 1A-2, the analog driver circuitry 116 is separated from the semiconductor die(s) having the integrated circuitry 114. As further shown in the illustrated embodiment, the second semiconductor dies 340 are electrically coupled to (a) corresponding ones of the first semiconductor dies 310 via second wire bonds 304 b and (b) corresponding ones of the second PIC chips 330 via third wirebonds 304 c. In other embodiments, the second semiconductor dies 340 can be electrically coupled to the first semiconductor dies 310 and/or the second PIC chips 330 via the package substrate 302 (e.g., via conductive traces or lines in the package substrate 302), and/or the second semiconductor dies 340 can be stacked on either the first semiconductor dies 310 or the second PIC chips 330 and directly attached via solder balls or other interconnect structures. In some embodiments, by locating the analog driver circuitry 116 and the integrated circuitry 114 on separate semiconductor dies, the first semiconductor dies 310 can be fabricated to have relatively smaller dimensions (e.g., compared to the semiconductor dies 110) and/or the first semiconductor dies 310 can be standard semiconductor dies well known in the art (e.g., conventional DRAM memory dies).

The first PIC chips 320 can have integrated circuitry 324, and the second PIC chips 330 can have integrated circuitry 334 and a light source 336 that are generally similar to the integrated circuitry 124, 134 and the light source 136, respectively, described in detail above with reference to FIGS. 1A-2. In the embodiment illustrated in FIG. 3, however, the integrated circuitry 324 includes a demultiplexer (e.g., a coarse wavelength division demultiplexer) such that optical signals from an external source can be received over only a single one of the optical fibers 306 a. Similarly, the integrated circuitry 334 of the second PIC chips 330 includes a multiplexer (e.g., a coarse wavelength division multiplexer) such that optical signals generated by the light sources 336 can be transmitted over only a single one of the optical fibers 306 b. In other embodiments, multiple multiplexed-signal-carrying optical fibers can be coupled to the PIC chips 320, 330.

In some embodiments, multiple semiconductor packages configured in accordance with the present technology can be incorporated into a larger semiconductor device (e.g., a memory device) to enable optical I/O data transmission to the semiconductor device. FIG. 4, for example, is a front view of a memory device 450 configured in accordance with an embodiment of the present technology. In the illustrated embodiment, the memory device 450 can be a memory module, such as a dual in-line memory module (DIMM) including a substrate (e.g., a printed circuit board (PCB) or the like) 452. A plurality of memories 400 can be coupled to the package substrate 452 via, for example, electrical connectors (e.g., solder balls). The memories 400 can be generally similar to the semiconductor packages 100, 200, and/or 300 described in detail above with reference to FIGS. 1A-3. In particular, the memories 400 can include one or more semiconductor dies (e.g., the semiconductor dies 110) each including integrated circuitry (e.g., the integrated circuitry 114) and/or driver circuitry (e.g., the analog driver circuitry 116), and one or more PIC chips (e.g., the PIC chips 120, 130) electrically coupled to the semiconductor dies and configured to (i) transmit and/or receive optical signals to/from the memories 400 and (ii) transmit and/or receive electrical signals to/from the semiconductor dies. In some embodiments, the memories 400 can be DRAM memories (e.g., DRAM memory dies, DRAM memory chips, DRAM memory packages, or the like). In some embodiments, the memories 400 can be identical (e.g., DRAM memory packages manufactured to have the same design and specifications), while in other embodiments the memories 400 can be different from each other (e.g., including different types of memory dies or different combinations of controller, logic, and/or memory dies).

In the illustrated embodiment, the memories 400 are arranged in a row on a first side or surface 453 of the package substrate 452. In other embodiments, the memories 400 can be arranged differently and/or can comprise a different number. For example, more or fewer than the illustrated eight memories 400 (e.g., four, ten, sixteen, twenty, etc.) can be arranged in any number of rows and/or columns, can be generally unaligned, etc. In some embodiments, the same or a different number of the memories 400 can be arranged on a second surface (not shown) of the package substrate 452 that is opposite the first surface 453. Any of the memories 400 on the second surface of the package substrate 452 can have the same or a generally similar configuration as the memories 400 on the first surface 453 of the package substrate 452. In some embodiments, the memory device 450 can include other electrical components (e.g., semiconductor components, integrated circuit components, etc.) coupled to the package substrate 452. For example, the memory device 450 can include one or more voltage regulators or power management integrated circuits (PMICs) and/or one or more registering clock drivers (RCDs) coupled to the package substrate 452.

In the illustrated embodiment, a single first (e.g., receive) optical fiber 406 a and a single second (e.g., transmit) optical fiber 406 b are optically coupled to individual ones of the memories 400. In some embodiments, each optical fiber 406 a, b can carry a multiplexed optical signal. In other embodiments, as set forth in detail above, multiple ones of the first optical fibers 406 a and/or multiple ones of second optical fibers 406 b can be optically coupled to individual ones of the memories 400. For example, the number of optical fibers 406 a, b can vary depending on the bandwidth of the memories 400, whether the PIC chips of the memories 400 are configured to (de)multiplex optical signals from/to the memories 400, the number of semiconductor dies in the memories 400, etc. In general, the optical fibers 406 a, b are configured to optically couple the memories 400 to external devices, circuitry, etc. In the illustrated embodiment, the optical fibers 406 a, b are coupled to optical connectors 458 that facilitate easy coupling of the optical fibers 406 a, b to external devices. In some embodiments, for example, the optical connectors 458 can be multi-fiber push on (MPO) connectors or other suitable connectors. While two optical connectors 458 are illustrated in FIG. 4, any number of optical connectors 458 can be used to bundle the optical fibers 406 a, b. In other embodiments, the optical connectors 458 can be omitted, and the optical fibers 406 a, b can be routed individually from the memory device 450 and optically coupled to external devices via other suitable methods.

As further shown in FIG. 4, the optical fibers 406 a, b can be bundled and routed along the first surface 453 of the package substrate 452 to the optical connectors 458. In some embodiments, an epoxy 454 (e.g., an epoxy glue) or other encapsulant can be deposited over all or a portion of the first surface 453 and the optical fibers 406 a, b (e.g., via a glob top method) to protect the optical fibers 406 a, b from damage and/or to inhibit tangling, knotting, etc., of the optical fibers 406 a, b. In the illustrated embodiment, the epoxy 454 does not encapsulate (e.g., does not cover or surround) the memories 400 while, in other embodiments, the epoxy 454 can encapsulate the memories 400 and/or cover the entire first surface 453 of the package substrate 452.

The memory device 450 further includes an edge connector 456 along a lower edge of the package substrate 452. The edge connector 456 includes a plurality of contacts 457 for connecting the memories 400 to external circuitry (not shown). In some embodiments, for example, the edge connector 456 can be used to releasably secure the memory device 450 in a corresponding DIMM slot in a host device (e.g., a motherboard). More particularly, in some embodiments, the edge connector 456 can electrically couple the memories 400 to an external power/ground source. However, the edge connector 456 need not connect the memories 400 to the host device for I/O transmission of data signals (e.g., during memory access operations), as the I/O transmission of data signals can be carried out optically via transmission over the optical fibers 406 a, b, as described in detail above. In some embodiments, data transmission to/from the memories 400 is carried out only over the optical fibers 406 a, b—and not over the package substrate 452. Put differently, in some embodiments, the package substrate 452 can only electrically couple the memories 400 to power/ground.

In some embodiments, a memory device according to the present technology can include an integrated waveguide that can reduce or eliminate the need for discrete optical fibers (e.g., the optical fibers 406 a, b). FIG. 5A, for example, is a partially schematic front view of a memory device 550 configured in accordance with another embodiment of the present technology and having an electro-optical substrate 552. The memory device 550 can include features generally similar to the features of the memory device 450 described in detail above with reference to FIG. 4. For example, the memory device 550 includes a plurality of memories 500 coupled to the electro-optical substrate 552, and an edge connector 556.

FIG. 5B is a side cross-sectional view of a portion of the electro-optical substrate 552 shown in FIG. 5A. Referring to FIG. 5B, the electro-optical substrate includes an electrical substrate (e.g., a PCB or the like) 562 and an optical layer (e.g., an optical routing layer) 564 on the electrical substrate 562. The electrical substrate 562 can include one or multiple layers of conductive material 565 (e.g., conductive traces, vias, etc.) and dielectric material 566 as is known in the art. The optical layer 564 can comprise a waveguide (e.g., a polymer waveguide) formed from one or more layers of optical material (e.g., silicon materials or compounds, polymers, dielectric materials, etc.). For example, referring to FIGS. 5A and 5B together, the optical layer 564 can include (i) first (e.g., receive) core portions 506 a, (ii) second (e.g., transmit) core portions 506 b, and (iii) a cladding portion 568. The core portions 506 a, b are shown schematically in FIG. 5A for the sake of clarity. In some embodiments, the cladding portion 568 can be formed from one or more materials having a lower refractive index than material(s) used to form the core portions 506 a, b such that light signals transmitted through the optical layer 564 are substantially confined to the core portions 506 a, b. In the illustrated embodiment, the core portions 506 a, b each have a generally rectilinear cross-sectional shape while, in other embodiments, the core portions 506 a, b can have other cross-sectional shapes (e.g., circular, polygonal, irregular, v-shaped, etc.).

In some embodiments, the optical layer 564 can be fabricated by photolithographic, laser direct writing, UV-laser direct imaging, nano-imprint lithographic, mosquito (e.g., needle-type liquid microdispensing), and/or other suitable deposition and patterning methods known in the art. In some embodiments, the optical layer 564 can be formed directly on the electrical substrate 562—for example, by depositing the one or more layers of optical material directly onto the electrical substrate 562 and processing the optical material via UV-laser direct imaging or another suitable process. In some such embodiments, the optical layer 562 is additively built or formed on the electrical substrate 562 such that the optical layer does not include any other substrate (e.g., a pre-formed substrate). In other embodiments, the optical layer 564 can be a separate structure that is formed on a separate substrate—such as, for example, a flexible substrate (e.g., a sheet or reel of plastic film) or a rigid substrate (e.g., glass or silicon)—and glued or otherwise affixed to the electrical substrate 562.

The memories 500 are (i) optically coupled to the core portions 506 a, b of the optical layer 564 and (ii) electrically coupled to the conductive material 565 of the electrical substrate 562. In the illustrated embodiment, optical connectors 558 are also optically coupled to the core portions 506 a, b of the optical layer 564. In operation, the core portions 506 a, b define optical receipt/transmission paths for the memories 500 while the electrical substrate 562 can provide power to the memories 500. In this manner, the optical layer 564 can reduce the need for discrete optical fibers (e.g., the optical fibers 406 a, b shown in FIG. 4) in the memory device 550. In some embodiments, short optical fibers can be used to optically couple the memories 500 and/or optical connectors 558 to the core portions 506 a, b of the optical layer 564. In other embodiments, the memories 500 and/or optical connectors 558 can be directly optically coupled to the optical layer 564 via vertical grating couplings that can be formed in the optical layer 564, or via other suitable structures or components. In some embodiments, optically transparent epoxies and/or index-matching gels can be used to close gaps (e.g., optically couple discrete components) between the optical layer 564, the memories 500, and/or the optical connectors 558. In other embodiments, the optical connectors 558 can be omitted and/or the optical layer 564 can be extended to provide an optical coupling to external devices. For example, the optical layer 564 can comprise a polymer waveguide having a longer length than the electrical substrate 562 such that the waveguide extends past the electrical substrate 562 to enable the waveguide to be routed to and directly coupled to another memory device or external device.

In some embodiments, data transmission to/from the memories 500 is carried out only over the optical layer 564—and not over the electrical substrate 562. Put differently, in some embodiments, the electrical substrate 562 only electrically couples the memories 500 to power/ground.

FIG. 6 is a schematic view of a system that includes a semiconductor package and/or memory device configured in accordance with embodiments of the present technology. Any one of the foregoing semiconductor packages and/or memory devices described above with reference to FIGS. 1-5 can be incorporated into any of a myriad of larger and/or more complex systems, a representative example of which is system 690 shown schematically in FIG. 6. The system 690 can include a memory device assembly 600, a power source 692, a driver 694, a processor 696, and/or other subsystems and components 698. The memory device assembly 600 can include features generally similar to those of the memory devices and semiconductor packages described above with reference to FIGS. 1-5. The resulting system 690 can perform any of a wide variety of functions, such as memory storage, data processing, and/or other suitable functions. Accordingly, representative systems 690 can include, without limitation, hand-held devices (e.g., mobile phones, tablets, digital readers, and digital audio players), computers (e.g., workstations, servers, etc.), vehicles, appliances, and other products. Components of the system 690 may be housed in a single unit or distributed over multiple, interconnected units (e.g., through a communications network). The components of the system 690 can also include remote devices and any of a wide variety of computer readable media.

From the foregoing, it will be appreciated that specific embodiments of the technology have been described herein for purposes of illustration, but that various modifications may be made without deviating from the disclosure. Accordingly, the invention is not limited except as by the appended claims. Furthermore, certain aspects of the new technology described in the context of particular embodiments may also be combined or eliminated in other embodiments. Moreover, although advantages associated with certain embodiments of the new technology have been described in the context of those embodiments, other embodiments may also exhibit such advantages and not all embodiments need necessarily exhibit such advantages to fall within the scope of the technology. Accordingly, the disclosure and associated technology can encompass other embodiments not expressly shown or described herein. 

I claim:
 1. A memory device, comprising an electro-optical substrate having a plurality of receive optical paths and a plurality of transmit optical paths, wherein the receive optical paths are optically separated from one another, and wherein the transmit optical paths are optically separated from one another, an optical connector optically coupled to the receive optical paths and the transmit optical paths, wherein the optical connector is configured to be optically coupled to an external device; and a plurality of memories carried by the electro-optical substrate, wherein the memories are electrically coupled to the electro-optical substrate, wherein individual ones of the memories are optically coupled to the optical connector via (a) a corresponding one or more of the receive optical paths and (b) a corresponding one or more of the transmit optical paths, wherein the receive optical paths and the transmit optical paths are different for each of the memories, and wherein the memories are configured to receive optical signals via the corresponding ones of the receive optical paths, transmit optical signals via the corresponding ones of the transmit optical paths and receive power via the electro-optical substrate.
 2. The memory device of claim 1 wherein the electro-optical substrate includes an electrical substrate and a waveguide defining the receive optical paths and the transmit optical paths, and wherein the memories are (a) electrically coupled to the electrical substrate and (b) optically coupled to the waveguide.
 3. The memory device of claim 2 wherein the waveguide comprises one or more layers of polymer material and does not include a pre-formed substrate.
 4. The memory device of claim 2 wherein the waveguide is affixed to the electrical substrate.
 5. The memory device of claim 2 wherein the electrical substrate is a printed circuit board (PCB).
 6. The memory device of claim 1 wherein the electro-optical substrate includes a grating coupling and a waveguide defining the receive optical paths and the transmit optical paths, and wherein the memories are optically coupled to the waveguide via the grating coupling.
 7. The memory device of claim 1 wherein the electro-optical substrate includes a waveguide defining the receive optical paths and the transmit optical paths, and wherein the memories are optically coupled to the waveguide via one or more optical fibers.
 8. The memory device of claim 1 wherein the optical connector is a multi-fiber push on (MPO) connector.
 9. The memory device of claim 1 wherein individual memories include (a) a first photon integrated circuit (PIC) chip optically coupled to the corresponding one of the receive optical paths and (b) a second PIC chip optically coupled to the corresponding one of the transmit optical paths.
 10. A duel in-line memory module DIMM, comprising: a substrate including a circuit board and optical routing layer on the circuit board, wherein the optical routing layer includes a plurality of receive optical paths and a plurality of transmit optical paths, wherein the receive optical paths are optically separated from one another, and wherein the transmit optical paths are optically separated from one another; an optical connector optically coupled to receive optical paths and the transmit optical paths, wherein the optical connector is configured to be optically coupled to an external device, and a plurality of memories electrically coupled to the circuit board, wherein individual ones of the memories are optically coupled to the optical connector via (a) a corresponding one of the receive optical paths (b) a corresponding one of the transmit optical paths, wherein the receive optical paths and the transmit optical paths are different for each of the memories.
 11. The DIMM of claim 10 wherein the optical routing layer is a polymer waveguide.
 12. The DIMM of claim 10 wherein the optical routing layer includes a pre-formed substrate, and wherein the optical routing layer is affixed to the circuit board.
 13. The DIMM of claim 10 wherein the optical routing layer includes two or more layers of polymer material having different refractive indices, and wherein the two or more layers of polymer material are formed directly on the circuit board.
 14. The DIMM of claim 10 wherein the circuit board includes an edge connector, wherein the memories are configured to receive power via the edge connector, and wherein the memories are configured to receive data signals only via the optical routing layer.
 15. A method of forming a memory device, the method comprising: forming an optical layer on an electrical substrate, wherein the optical layer includes a plurality of receive optical paths and a plurality of transmit optical paths, wherein the receive optical paths are optically separated from one another, and wherein the transmit optical paths are optically separated from one another; optically coupling an optical connector to the receive optical paths and the transmit optical paths, wherein the optical connector is configured to be optically coupled to an external device; electrically coupling a plurality of memories to the electrical substrate; and optically coupling individual ones of the memories to the optical connector via (a) a corresponding one of the receive optical paths and (b) a corresponding one of the transmit optical paths, wherein the receive optical paths and the transmit optical paths are different for each of the memories.
 16. The method of claim 15 wherein forming the optical layer includes depositing one or more layers of polymer material directly onto the electrical substrate.
 17. The method of claim 16 wherein forming the optical layer includes patterning the one or more layers of polymer material to form a polymer waveguide.
 18. The method of claim 15 wherein the optical layer includes a waveguide, and wherein forming the optical layer includes affixing the waveguide to the electrical substrate.
 19. The method of claim 18 wherein the waveguide includes a flexible substrate.
 20. The method of claim 18 wherein the waveguide includes a rigid substrate. 